Predetermined processing length in a numerically controlled machine tool

ABSTRACT

A device for nibble and planing machines for the automatic division of a predetermined processing length in a numerically controlled machine tool wherein the standard step is predetermined from the outside and is not permitted to fall short of a specific value determined by technical requirements comprises a comparison device. A difference circuit supplies a signal representing the remaining processing length (s - x) to the comparison device. A step length counter supplies a signal representing the step length to the comparison device. The comparison device produces an output signal for reducing the step length to divide the remaining processing length into p steps of substantially equal length when the comparison result indicates that the remaining processing length is shorter than p times a longer standard step ( Delta s).

United States Patent 1 1 Weber et al.

[ PREDETERMINED PROCESSING LENGTH IN A NUMERICALLY CONTROLLED MACHINE TOOL 1 Oct. 16, 1973 Primary Examiner-Eugene G. Botz Attorney-Arthur E. Wilfond et a1.

[75] Inventors: Fritz Weber, Erlangen; Peter Schiewek, Eltersdorf; Dieter 5 7] ABSTRACT Kremper Erlangen of Germany A device for nibble and planing machines for the auto- [73] Assignee: Siemens Aktiengesellschaft, Berlin, matic division of a predetermined processing length in Germany a numerically controlled machine tool wherein the standard step is predetermined from the outside and is [22] Flled' 1971 not permitted to fall short of a specific value deter- [21] App]. No.: 191,161 mined by technical requirements comprises a comparison device. A difference circuit supplies a signal representing the remaining processing length (s x) [52] to the comparison device. A step length counter 51 I t Cl GOSb 19/40 supplies a signal representing the step length to the d 151 11 I comparison device. The comparison device produces e 0 CT i f an output signal for reducing the step length to divide 90/24 318/696 the'remaining processing length into p steps of substantially equal length when the comparison result indicates that the remaining processing length is shorter [56] UNITE S S E T T E S SZqFENTS than p times a longer standard step (As). 2,817,775 12/1957 7 Rosenberg et al. 235/151.11 5 Claims, 2 Drawing Figures END SWITCH lfi I ELECTRUHYIIRAULIC (INTERPULMUR I STEPPING MUTUR p y '7 l x t t 1 REVERSE 2 COUNTER I t: I

- fsm REGISTER l 1 LENGTH COUNTER CUMPARISUN DEVICE PREDETERMINED PROCESSING LENGTH IN A NUMERICALLY CONTROLLED MACHINE TOOL The invention relates to a device for the automatic division of a predetermined processing length or distance in a numerically controlled machine tool. More particularly, the invention relates to a device for the automatic division of a predetermined processing distance in a numerically controlled machine tool wherein a standard step assumed from the outside is not permitted to fall short of a specific value determined by technical requirements. The device is particularly intended for nibble machines.

When a numerical control is included in nibble machines which are used, for example, to punch out switchboards, control boards, control panels, and the like, the portion of a contour to be processed is programmed in a setof perforated strips. The entire distance or length is then divided into equal parts and punching is effected after the start of each step.

The component part to be worked on, that is, the length of the step, results from the programmed travel speed of the tool or the workpiece and the time for the control pulses to travel from the control to the drive of the machinev tool. The release of the control pulses, which are normally produced by an interpolator, is usually effected via an electronic end switch which releasesthe interpolator for as long as the tool of the machine is in the range of the upper dead-center position.

The release time together with the programmed speed result in the travelled distance from stroke to stroke, that is, the step of the machine. During the nibbling'of various lengths or distances it is almost inevitable, when constant step lengths are required, I

that a remnant of the length will remain at the end of each interpolator section and, under certain circumstances, may be vso short that the tool may give way or turn aside during nibbling toward the preceding punch hole. As a result, the tool may break.

A similar problemof section division also occurs in planing machines-where care must be taken that the last chip or shaving to be planed does not fall short of a specific thickness. I 1

The same problem may haveto befaced in a machine tool with adaptive regulation. For. technical reasons such .as, for example, cutting speeds, it is necessary, with respect to turning and milling machines, for example, thata minimal chipbe removed during the last processingpassage. v

- It-is an objectof the present invention to so vary the step length inmachine tools of the aforedescribed type, that particularly the'last step will I, not fall shortof a value determined by technological requirements.

To accomplish this, and in accordance with the invention,the device for the automatic division of a predetermined length in a numerically con trolled machine tool comprises a comparison device whose output signal subdivides the remaining processing length or distance into p steps of almost equal length if the remaining processing length or distance is shorter than p steps of the longer standard or normal step. Normally, it would suffice to provide the shortening of the steps for the last four or five steps.

The device may be so constructed that the remaining processing distance is transferred, following each step, from a processing distance datum and pilot difference counter to a register. The zero signal of the counter indicates the end of the processing distance. The indication of the register and the indication of a step length counter are supplied to the comparison device. The transfer of the respective remnant processing distance to the register is then omitted from the time the step length is shortened.

In accordance with the invention, a device for nibble and planning machines for the automatic division of a predetermined processing length in a numerically controlled machine tool wherein the standard step is predetermined from the outside and is not permitted to fall short of a specific value determined by technical requirements, comprises comparison means. Difference means supplies a signal representing the remaining processing length (s x) to the comparison means. Step length means supplies a signal representing the step length to the comparison means. The comparison means produces an output signal for reducing the step length to divide the remaining processing length (s x) into p steps of substantially equal length when the comparison means provides a comparison result which indicates that the remaining processing length (s x) is shorter than p times a longer standard step (As).

The comparison means produces an output signal when the comparison result indicates that the remaining processing length (s x) is shorter than four standard steps.

The difference means comprises a processing length datum-pilot difference counter producing a zero signal at the end of the processing length and a register connected to the comparison means. The difference counter transfers a signal indicating the remaining processing length to the register after each step. The step length means comprises a step length counter connected to the comparison means. The difference counter comprises a reverse counter. The dividing means includes means for preventing the transfer of a signal from the difference counter to the register of the difference means when the step length is shortened.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, wherein: p FIG. I is a schematic diagram for explaining the division of the length; and 1 FIG. 2 is a block diagram of an embodiment-of the device of the invention forthe automatic division of a predetermined processing length in a numerically'controlled machine tool.

FIG. 1 shows a length or'distance s. The normal or standard step length As is fixed'from the outside by the nibble machine. The circuit of the invention, as shown in FIG. 2, varies several of the last step lengths, so that the last step in the X direction-cannot fall below a predetermined. value.

. In FIG. 2, an end switch 6 is located in the stroke path of a numerically controlled machine (not shown in FIG. 2). The end switch 6 releases an interpolator 1. The interpolator l delivers for each step in 'the X direction a specific number of pulses to-an electrohydraulic stepping motor 7. The motor 7 effects the' feeding of the tool (not shown in FIG. 2) in theX direction.

At the same time, the interpolator l feeds the pulses to a digital processing distance datum and pilot difference or reverse counter 2. The counter .2 is preadjusted, at the start of the processing length or distance, to the entire length s. At the end of each count,

the'indication s nAs of the counter 2 is transferred to a register 3 via a switch 8. In the counter 2 indication s nAs, n is the number of steps already travelled.

The interpolator 1 also simultaneously supples pulses to a counter 4, which determines the respective ste length As.

After each tool or punch stroke, the indication of the register 3 is compared with the predetermined step length As in the comparison device 5. If, towards the end of the procesing length or distance, the indication s nAs of the register 3 is lower than a predetermined number p times the indication of the step length counter 4, the comparison device 5 produces a command signal to shorten the length of the steps. The indications of the register 3 and step length counter 43 are derived with simplicity by deriving the signals at specific stages of said register and said counter.

To shorten the length of the steps, as command by the comparison device 5, the switch 8 blocks, for the next step, the transfer of the indication of the reverse counter 2 to the register 3. This may be accomplished by any suitable means such as, for example, a relay winding 9 connected to the output of the comparison device 5 and operating the switch 8. During the nextsucceeding step, the interpolator l delivers pulses to the stepping motor 7 and the step length counter 4, starting from zero, until p times the indication of said counter is higher than the remnant value of the register 3, which remains constant. Thereupon, the interpolator l is blocked by a signal from the comparison member 5. This procedure continues until the end of the processing.

As a result of the aforedescribed operation, the entire remaining or remnant length or distance s nAs is subdivided into p parts. During the last step, a length is travelled per step. 7 p g If theresult is not a whole number, this will only mean that the last step will be shorter by some percent than the preceding steps, ifthe counter 2 reaches an indication of zero, but will, inany event, still be completely within-the tolerable range. I I, This maybe illustrated by a simple example. It is assumed that the standard step As 40 pulses 4 mm, the predetermined number of steps is p 4, and the remaining p'rocessing length or distance s nAs 161 pulsesl The coin'parisonshowsthat 16l is greater than 4 times 40 or1 l60, that is, thev standard step can stillbe carried out. -After the standard step, the new indication of the "register 3 is '121 pulses. If the step length counter 4 is again timed, the result at its position As 31 shows that 4 times 31' 124 is greater'than 121, which is the The output signal of the comparison device 5 opens the switch 8. During the next step, the comparison shows that when the count indication of the step length counter 4 is 31, 4 times 31 is 124, which is greater than 121. Thus, the new step length As is also 31. This is followed by a step As with 31 pulses and a last step As 1. A device for nibble and planing machines for the automatic division of a predetermined processing length in a numberically controlled machine tool wherein the standard step is predetermined from the outside and is not permitted to fall short of aspecific value determined by technical requirements, said device comprising comparison means; difference means for supplying a signal representing the remaining processing length (s x) to the comparison means; step length means for supplying a signal representing the step length to the comparison means, said comparison means producing an output signal for reducing the step length to divide the remaining processing length (s 1:) into p steps of substantially equal length when said comparison means provides a comparison result which indicates that the remaining pocessing length (s x) is shorter than p times a longer standard step (As).

2. A device as claimed in claim 1, wherein the comparison means produces an output signal when the comparison result indicates that the remaining pro'cessing length (s x) is shorter than four standard steps. 3. A device as claimed in claim 1, wherein the difference means comprises a processing length datum-pilot difference counter producing azero signal atthe end of the processing length and a register connected to the comparison means, said differencev counter transferring a signal indicating the remaining processing length to the register after each step, and the step length means comprises a step length counter connected to' t he coni- Parison means; A v

4. A device as claimed claim 3','wh'r einthediffer# ence counter comprises a reverse counter, 5. A device as claimed in claim 3 wherein the dividing means includes means for preventing the transfer of I a signal from the difference counter to the register of the difference means when the step length is shortened;

' s a: Y

P021050 1 "TTED $-ATES i 'LTEI T QFFiCE (5 69) CERTAFECATE @F CQRLECTIC'B.

Patent No. 3,7 3 I Dated October 16, 1973 Inventor(s) FRITZ WEBER ET AL It is certified thaterror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, there should be included: I

+Foreign ApplicationPriority Data October- 28, 1970 Ger-many. .P 20 52 757.5"

Signed and sealed this 16th day of April 19%,.

(SEAL) Attest:

EDWARD I'LFLL'JT'GHERJR. C. MARSHALL DAN N Attesting Officer Commissioner of- Patents Invento-:(s) FRITZ WEBER ET AL It is certified that-error appears in the above-idertified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, there should be included:

-For'e ign ApplicationPriority Date I Germany........' .P 2O 5 757-5-- October' 28, 1970 Signed and sealed this 16th day of April 1971 (SEAL) Attest: I

- c MARSHALL D NN Commissioner of Patents EDWARD I'LFLSTGHERJR; Attesting Officer 

1. A device for nibble and planing machines for the automatic division of a predetermined processing length in a numerically controlled machine tool wherein the standard step is predetermined from the outside and is not permitted to fall short of a specific value determined by technical requirements, said device comprising comparison means; difference means for supplying a signal representing the remaining processing length (s - x) to the comparison means; step length means for supplying a signal representing the step length to the comparison means, said comparison means producing an output signal for reducing the step length to divide the remaining processing length (s - x) into p steps of substantially equal length when said comparison means provides a comparison result which indicates that the remaining processing length (s - x) is shorter than p times a longer standard step ( Delta s).
 2. A device as claimed in claim 1, wherein the comparison means produces an output signal when the comparison result indicates that the remaining processing length (s - x) is shorter than four standard steps.
 3. A device as claimed in claim 1, wherein the difference means comprises a processing length datum-pilot difference counter producing a zero signal at the end of the processing length and a register connected to the comparison means, said difference counter transferring a signal indicating the remaining processing length to the register after each step, and the step length means comprises a step length counter connected to the comparison means.
 4. A device as claimed in claim 3, wherein the difference counter comprises a reverse counter.
 5. A device as claimed in claim 3, wherein the dividing means includes means for preventing the transfer of a signal from the difference counter to the register of the difference means when the step length is shortened. 